According to a new study from fertility researchers at the State University of New York at Stony Brook, laptops can make men infertile by heating up their scrotum when the computer is on their lap.

The potential risk comes from the heat generated by the laptop computer and the close position of one’s thighs when balancing the computer on one’s lap, the researchers found. This heat is transferred to the scrotum, where the temperature can rise several degrees, putting users within the danger zone for testicular dysfunction.

Beer bellies may take a toll on men below the belt, not just around it. Men who weigh too much are more likely to have poor sperm quality, research on nearly 1,600 young Danish men has found. Being too thin is a problem, too.

Women don’t get off the hook. Though it’s long been known that very overweight women have trouble conceiving naturally, a large new study confirms they also are less likely to become pregnant even when embryos are fertilized in lab dishes and placed in their wombs.